CONGENITAL HIGH AIRWAY OBSTRUCTION SYNDROME [CHAOS ] - An antenatal ultrasound diagnosis

CHAOS  -  Refers to a rare & fatal congenital anomaly seen due to obstruction of upper airway  in fetal life either due to oropharyngeal or neck masses , & or most common being laryngeal / tracheal atresia.  The risk of associated  chromosomal anomaly is very rare , and overall the prognosis is considered to be poor.  However some cases can be treated with neonatal intervention such as ,  ex -  utero – intrapartum treatment By- Dr.Subhash Tailor

M.D.[ Radiology]

Bhilwara [Rajasthan]

Antenatal ultraound diagnostic criterias are  -

1.       Dilated fluid filled trachea / bronchi distal to obstruction

2.      Bulky echogenic lungs

3.      Diaphragmatic flattening and or inversion

4.      Midline positioned & compressed fetal heart

5.      Fetal ascites  and Anasarca

6.      Fetal neck mass , if any

7.      Polyhydramnios

A case of CHAOS diagnosed antenatally with  ultrasound at about 17 weeks of gestation is being presented here featuring classical findings . 

Case details -  A 28 yrs old  2^nd gravida was asked for anomaly scan .  Her previous  pregnancy was stated to be  normal . 

AT  USG - fetal chest showed bulky echogenic lungs with dilated and fluid filled trachea and proximal bronchi.  The domes were also inverted .  Fetal heart was seen narrowed , midline positioned and appeared compressed between bulky echogenic lungs .  Fetal hydropic changes were also seen as skin / soft tissue edema and ascites [ likely due to fetal heart failure ].  See figures 1 to 4  

The liquer amnio was average in this case .  These antenatal ultrasound  findings were  diagnostic of  CHAOS . The parents decided to terminate the pregnancy .

                                                                 

Figure 1-  Fetal coronal  thoracic  & axial head scans shows bulky echogenic both lungs , dilated fluid filled trachea & bronchi with inverted diaphragms ,& scalp edema .

Figure 2- Coronal US scan of fetal chest including part ofupper  abdomen - shows enlarged echogenic lung masses & mild ascites

Figure 3- Fetal thorax  coronal color Doppler scan shows fluid filled dilated trachea –bronchi [color void]

Figure 4 – TS fetal thorax shows midline narrow compressed heart[arrows]